Structures of water jet nozzles for use with a loom are disclosed in Japanese Utility Model Unexamined Publication (KOKAI) Nos. 61-155386 and 62-88779.
In recent years, as disclosed in these publications, a dominant type of water jet nozzle incorporates a stabilizer for straightening water flow of the water jet nozzle with speed-up in an automatic loom.
This type of prior art water jet nozzle, as shown in FIG. 5, is so constructed that an orifice E and a needle F inserted concentrically with the orifice E are provided at a top of a body D formed with a pool C communicating with a water injection hole B of a holder A. The structure of the water jet nozzle is such that the water injected via injection hole B of the holder A jets out from a gap between the orifice E and the needle F. The water jet nozzle performs a function to intermittently feed, between warps stretched from a tip of the needle F to an unillustrated loom, a weft yarn charged in from a cavity G of the needle F.
When feeding out the weft yarn, it is required that a jet flow formed in the path from the water injection hole B to the gap between the orifice E and the needle be rectified as much as possible.
For this straightening, a resinous stabilizer H having a construction shown in FIG. 6 is so disposed as to be contiguous to a rear end of the orifice E composed of hardened steel.
The resinous stabilizer H is manufactured simply by injection molding and also simply assembled by setting it in a space at a rear part of the orifice E made of hardened steel. The stabilizer H exhibits a remarkable effect for a loom having a weftwise feeding number of approximately 400-750 times/min under a water pressure of about 25 kg/cm.sup.2.
With the further advancement of speeding up the loom in recent years, working conditions oriented thereto are that water pressure is 30-40 kg/cm.sup.2 ; water flow rate reaches 30 -40 m/sec.; and the number of insertions of weft yarn exceeds 1000 times/min.
In the water jet nozzle equipped with a resinous stabilizer, the material of which the stabilizer is formed is insufficient in its hardness and strength, resulting in an intensive wear caused by the water flow and in a short life span thereof. Besides, it is impossible to set the thickness of a blade unit to 0.2 mm or under. At a high flow rate of more than 30 m/sec., the water pressure drops due to fluid resistance, and the weftwise feeding number is limited to 750 times/min. Under such conditions, it is absolutely impossible to achieve higher-speed feeding of the weft yarn.
In addition, vibrations and swirls are caused due to deformation of the stabilizer itself when the water flows at a high velocity. This situation in turn makes the insertions of weft yarn irregular, and there arise problems of causing both a drop in availability factor concomitant with a stagnation of the loom as well as a decline in the quality of fabrics woven.
The conventional water jet nozzle generates water jets from the orifice and needle, and the unit for feeding out the weft yarn is made at best of a hardened steel. Hence, wear resistance and corrosion resistance are not sufficient, as a result of which the device decreases in its life span and associated components have to be replaced. Not only does the resinous stabilizer conceived as a replaceable component decrease in availability factor, but also the loom itself is thereby reduced in the same factor.
In order to improve the wear resistance, a structure of embedding a cylindrical ceramic body in an inside diametrical part of the tip of the conventional needle made of hardened steel and bonding it thereto has been proposed. This structure, however, presents the problem of the ceramic body falling off during use.